Nature publishes a study by climate scientists Raymond Bradley, Michael Mann, and Malcolm Hughes concluding that the last few decades were warmer than any comparable time period in the last 1,000 years. Their study shows that the pace of warming was most dramatic during the last century. The authors identified the increase of greenhouse gases in the atmosphere as the dominant factor in the observed increase in global temperatures. [Nature, 4/23/1998 ; San Francisco Chronicle, 6/23/2006]

The journal Science publishes a study suggesting that a major factor in rising ocean temperatures is likely “the increase of anthropogenic gases
in Earth’s atmosphere.” The study’s conclusions are based on analysis of historical ocean data pertaining to the latter half of the twentieth century. These findings are supported by results that were produced by an atmosphere-ocean general circulation model. [Levitus et al., 2001 ]

The National Research Council issues a report on global climate change that was commissioned by the White House. The opening paragraph of the document reads: “Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability. Human-induced warming and associated sea level rises are expected to continue through the 21st century. Secondary effects are suggested by computer model simulations and basic physical reasoning. These include increases in rainfall rates and increased susceptibility of semi-arid regions to drought. The impacts of these changes will be critically dependent on the magnitude of the warming and the rate with which it occurs.” [Committee on the Science of Climate Change, National Research Council, 2001; CBS News, 6/19/2003; Boston Globe, 6/20/2003]

The Journal of Climate publishes a paper by hurricane expert Robert Tuleya and NOAA climate scientist Thomas Knutson suggesting that an increased concentration of carbon dioxide in the atmosphere may increase the intensity of hurricanes. Knutson’s study is based on computer analysis performed at the Commerce Department’s Geophysical Fluid Dynamics Laboratory in Princeton, N.J. The two scientists created some 1,300 virtual hurricanes using a more powerful version of the same supercomputer simulations that the NOAA uses to track and predict the behavior of real hurricanes. The New York Times reports that according to independent experts “this study is particularly significant… because it used half a dozen computer simulations of global climate, devised by separate groups at institutions around the world.” MIT climate scientist Kerry A. Emanuel says Knutson’s study “is by far and away the most comprehensive effort” to analyze the issue using computer simulations. [New York Times, 9/30/2004; Tuleya and Knutson, 2005 ]

The journal Nature publishes an article by MIT climatologist Kerry Emanuel suggesting that rising sea temperatures are producing stronger hurricanes. His study found that a combined measure of duration and wind speeds among North Atlantic hurricanes and North Pacific cyclones has almost doubled since the 1970s. “The best way to put it is that storms are lasting longer at high intensity than they were 30 years ago,” says Emanuel. [Emanuel, 2005; USA Today, 7/31/2005]

A study published in the Proceedings of the National Academy of Sciences (PNAS) concludes that there is an 84 percent chance that human activity is responsible for rising sea surface temperatures (SST). Climate scientist Tom Wigley, one of the study’s authors, says data from 22 different computerized climate change models showed “exceptional correlation” between human activity and climate change. The only plausible explanation for the dramatic increase in sea surface temperatures is deforestation and the burning of fossil fuels. “There is less than a one percent chance that the changes in SST could be the result of non-human factors,” Wigley explains. The paper also finds that higher sea surface temperatures are increasing the frequency and intensity of storms in the Atlantic and Pacific oceans. [Inter Press Service, 9/12/2006; Boston Globe, 9/12/2006; Santer et al., 9/19/2006]

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